A women attend a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. Police say more than 300 girls and young women were abducted mid-April from Chibok Government Girls Secondary School, of whom some 53 girls are known to have escaped. (AP Photo/ Sunday Alamba)

A women attend a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. Police say more than 300 girls and young women were abducted mid-April from Chibok Government Girls Secondary School, of whom some 53 girls are known to have escaped. (AP Photo/ Sunday Alamba)

Women attend a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. Police say more than 300 girls and young women were abducted mid-April from Chibok Government Girls Secondary School, of whom some 53 girls are known to have escaped. (AP Photo/ Sunday Alamba)

Femi Falana, a lawyer and human rights activist, centre, leads a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. Police say more than 300 girls and young women were abducted mid-April from Chibok Government Girls Secondary School, of whom some 53 girls are known to have escaped. (AP Photo/ Sunday Alamba)

Women attend a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. Police say more than 300 girls and young women were abducted mid-April from Chibok Government Girls Secondary School, of whom some 53 girls are known to have escaped. (AP Photo/ Sunday Alamba)

A woman attends a demonstration calling on the government to increase efforts to rescue the 276 missing kidnapped school girls of a government secondary school Chibok, in Lagos, Nigeria, Monday, May 5, 2014. Leader of a protest march Saratu Angus Ndirpaya of Chibok town, said that Nigeria’s First Lady ordered her and another protest leader to be arrested Monday, and expressed doubts there was any kidnapping and accused them of belonging to the Islamic insurgent group blamed for the abductions. (AP Photo/ Sunday Alamba)

Buy AP Photo Reprints

LAGOS, Nigeria (AP) â€” Nigeria’s Islamic extremist leader is threatening to sell the nearly 300 teenage schoolgirls abducted from a school in the remote northeast three weeks ago, in a new videotape received Monday.

Abubakar Shekau for the first time also claimed responsibility for the April 15 mass abduction.

He threatened to attack more schools and abduct more girls.

“I abducted your girls,” said the leader of Boko Haram, which means “Western education is sinful.”

He described the girls as “slaves” and said “By Allah, I will sell them in the marketplace.” The hour-long video starts with fighters lofting automatic rifles and shooting in the air as they chant “Allahu akbar!” or “God is great.”

It was unclear if the video was made before or after reports emerged last week that some of the girls have been forced to marry their abductors â€” who paid a nominal bride price of $12 â€” and that others have been carried into neighboring Cameroon and Chad. Those reports could not be verified.

In the video, Shekau also says the students “will remain slaves with us.” That appears a reference to the ancient jihadi custom of enslaving women captured in a holy war, who then can be used as sex slaves.

“They are slaves and I will sell them because I have the market to sell them,” he said, speaking in the Hausa language of northern Nigeria.

The video was reviewed by The Associated Press and both the face and the voice of the leader of Boko Haram were recognizable.

Shekau brushed off warnings that the abductions could be an international crime, saying in English, as if to reach his accusers in the international community: “What do you know about human rights? You’re just claiming human rights (abuses), but you don’t know what it is.”

An intermediary who has said Boko Haram is ready to negotiate ransoms for the girls also said two of the girls have died of snakebite and about 20 are